air handler - Contractor Talk - Professional Construction and Remodeling Forum

mikeybobo · 11-28-2008, 10:07 AM

carpenter here that knows nothing about hvac

I'm renovating my own house, and my father is a union tin knocker is doing my hydro air system. Him and his boss both are suggesting a first co air handler for my system, I dont remember the size off hand, but the two of them say not to go with a variable speed due to reliability issues and "the repairs if needed are more" than a single speed handler. I asked the hvac guys I've run across on our jobs at work as well as a neighbor of mine who is an energy star rep and they all say you are crazy not to go with the variable speed. First Co has the correct size for me in variable and not variable speed. Any feedback would be appritiated

flashheatingand · 11-28-2008, 12:52 PM

I agree with Pops. I went to a seminar at the local supply house where an engineer from A.O. Smith was talking about motors. One thing I distincly recall is that when a V.S. motor is matched to a multi speed motor, and they both are running at the same speed, the V.S. is only 7% more energy efficient.

The V.S. motors are expensive to replace. Maybe it would be favorable to go with v.s. if you plan on running the fan 24/7 but, if it were my friend, I would try to steer them away form v.s. I think it is a bunch of malarky.

Also, as I recall in reading about motors, a single speed fan is the most efficient type of motor because there is less "windings" in the motor.

Fla Air Temp · 11-28-2008, 03:33 PM

The variable speed motor works well when you hook up all the other things that go along with the system, like the humidity control and the outdoor temp sensor to let the motor run with the system instead of being just a motor. If you don't want that stuff, just get a multi-speed motor. Save yourself a few bucks.

mikeybobo · 11-28-2008, 07:52 PM

ok, thanks for the info

spheatandair · 12-03-2008, 09:43 PM

I am not sure what you mean by "hydro" air system. I assume you mean you are connected to a boiler or possibly thermal solar assised(hint, something to think about) Hot water. You could use the vari. speed to obtain the proper speed to maintain proper air temp rise. allowing you more time the unit could run changing out the air in the house more often and getting a more even temp in the whole home.

flashheatingand · 12-03-2008, 10:34 PM

Why can't you get a "even temperature rise with a multi-speed motor just set the speed at the correct setting? I don't know, I have never seen any actual temp. sensors in the furnaces so, I don't know how the machine knows how to ramp up and down due to temps. I have never seen any guages that measure static press to guarantee the actual cfm's as claimed. I think it ramps up and down due to some "time logic"

I just think that v.s. is an upsell that is a disservice to the customers. I can be persuaded. But I haven't heard anything concrete to tell me any differently.